What is the Baltic Sea anomaly really?

A sonar image from a 2011 treasure hunt

In the summer of 2011, two Swedish treasure hunters, Peter Lindberg and Dennis Åsberg, were searching for shipwrecks in the Gulf of Bothnia, the northern arm of the Baltic Sea between Sweden and Finland, when their side-scan sonar recorded a round shape on the seabed. Their team, Ocean X, said the shape was about 60 meters (200 feet) across and sat roughly 91 meters (300 feet) down. Geologists who later examined samples from the site concluded it is very likely a natural rock formation shaped by glaciers, not a sunken craft of any kind.

What the sonar and dive images actually show

The picture that made the story famous was not a raw sonar return but a version with a shape traced over it: the sonar image "looks like a spaceship only because the Ocean X team drew a Millennium Falcon-shape outline around it," NBC News reported, referencing the ship from the "Star Wars" films. When Ocean X returned to film the site directly in 2012, the footage showed a low, cracked rock formation on the seabed. No published photograph has ever shown a hull, hatch or any machined surface; every widely shared image is either a sonar rendering or footage of ordinary-looking rock.

During the 2012 dive, Ocean X also described "an entrance in the top of the UFO-like object," including what they called an egg-shaped hole, and pointed to rocks they said were charred and covered in soot. Geologists who reviewed the claims called the description "completely unwarranted," noting that "practically all rocks that have been underwater for a long time are black," regardless of whether they were ever burned. The divers never released a photograph of the hole itself, even though they had described it as the most striking part of the site.

A site that seemed to behave strangely

Ocean X did not just claim an unusual shape; they described the site behaving strangely. One of the team's divers said, "Anything electric out there — and the satellite phone as well — stopped working when we were above the object," and reported the equipment worked again once the boat moved away. Researcher Jonathan Hill raised a separate concern about motive, pointing out that Lindberg was "already making plans to take 'wealthy tourists' down in his submarine to view the object," and asking, "If it turned out to be a pillow basalt and not a 'mysterious UFO-like object,' Mr. Lindberg wouldn't have much of a business plan, would he?"

A second claim that did not hold up

In 2012, media reports said Ocean X had found a second, smaller disc-shaped object about 200 meters from the first. That claim did not survive scrutiny: NBC News found "the image of the second mysterious object used in current reports is actually a duplicate of the original sonar image," and when a genuine image finally surfaced, it "more closely resembles a lumpy eggplant or a blueberry muffin." A Woods Hole researcher added that the side-scan sonar Lindberg used "is not very reliable" for flat seafloor features and that there was "evidence the sonar was not calibrated properly."

What the rock samples showed

To settle the question, Ocean X handed rock samples from the site to Volker Brüchert, an associate professor of geology at Stockholm University, for independent analysis. He reported that "most of the samples they have brought up from the sea bottom are granites and gneisses and sandstones" — ordinary rock types, not metal, not anything manufactured, and "exactly what one would expect to see in a glacial basin," which the Baltic Sea is.

A natural, glacial explanation

Brüchert explained the likely mechanism: "Because the whole northern Baltic region is so heavily influenced by glacial thawing processes, both the feature and the rock samples are likely to have formed in connection with glacial and postglacial processes," he said, adding, "Possibly these rocks were transported there by glaciers." Other geologists suggested the rounded shape was consistent with a pillow basalt, a natural volcanic rock formation that is unusual but well documented. Marine geologist Dan Fornari cautioned separately that "the sonar image has numerous artifacts in it that make it difficult to interpret, and I would not place too much confidence in any interpretation until a better processing is done."

What is still debated

Even Peter Lindberg, the diver who first publicized the find, did not insist on an artificial origin. Asked by ABC News to weigh a natural-formation theory against a proposed link to a 19th-century Russian disc-shaped warship called the Novgorod, which at 35 to 37 meters across was too small to match, he said, "it is a bigger chance that the circle being a natural phenomena." What remains unsettled is narrower than the tabloid version of the story: no independent, peer-reviewed survey of the site has been published, so the natural explanation rests on one geologist reading samples the divers chose to bring up, not a full scientific expedition.

Verdict

Real or Legend stamps the UFO reading of the Baltic Sea anomaly debunked. Every claim that pointed to something built or alien — the shape, the equipment failures, the second disc, the "charred" rocks — either turned out to be an artifact of sonar and imagination or has never been backed by evidence, while the one independent rock analysis on record points to granite, gneiss and sandstone left by glaciers. The anomaly is very likely a piece of the Baltic seafloor, not a piece of anything else.